--gtest_filter should only change NumParallelJobs' default value

BUG=741927,735587

Change-Id: Ib95bd85e2f1ad14e27ba8fa76f8b52f8e137e830
Reviewed-on: https://chromium-review.googlesource.com/569159Reviewed-by: Paweł Hajdan Jr. <phajdan.jr@chromium.org>
Commit-Queue: Mostyn Bramley-Moore <mostynb@opera.com>
Cr-Commit-Position: refs/heads/master@{#486773}

base/test/launcher/test_launcher.cc

@@ -1193,13 +1193,10 @@ size_t NumParallelJobs() {
   CommandLine* command_line = CommandLine::ForCurrentProcess();
   CommandLine::SwitchMap switches = command_line->GetSwitches();
 
-  size_t jobs = 0U;
+  if (command_line->HasSwitch(switches::kTestLauncherJobs)) {
+    // If the number of test launcher jobs was specified, return that number.
+    size_t jobs = 0U;
 
-  if (command_line->HasSwitch(kGTestFilterFlag) && !BotModeEnabled()) {
-    // Do not run jobs in parallel by default if we are running a subset of
-    // the tests and if bot mode is off.
-    return 1U;
-  } else if (command_line->HasSwitch(switches::kTestLauncherJobs)) {
     if (!StringToSizeT(
             command_line->GetSwitchValueASCII(switches::kTestLauncherJobs),
             &jobs) ||
@@ -1207,10 +1204,13 @@ size_t NumParallelJobs() {
       LOG(ERROR) << "Invalid value for " << switches::kTestLauncherJobs;
       return 0U;
     }
-
-    return jobs;
+  } else if (command_line->HasSwitch(kGTestFilterFlag) && !BotModeEnabled()) {
+    // Do not run jobs in parallel by default if we are running a subset of
+    // the tests and if bot mode is off.
+    return 1U;
   }
 
+  // Default to the number of processor cores.
   return base::checked_cast<size_t>(SysInfo::NumberOfProcessors());
 }